Early results showed Nauseda won about three-quarters of the vote, well ahead of her rival, Prime Minister Ingrida Simonytė, from the ruling Fatherland Union party.
Lithuanian President Gitanas Nauseda declared victory in a runoff election on Sunday after a campaign centered on European security concerns.
“Your vote gives me a mandate. It's a strong mandate. The trust you have given me is great and it certainly obliges me to act,” he said in his victory speech.
Lithuania is 2022 Russian invasion Nauseda indicated that support would continue into her new presidential term.
According to an ELTA/Bartijos Tirimaj poll conducted earlier this year, more than half of Lithuanians believe that a Russian attack on the country is possible, but Moscow has consistently denied these concerns.
“My guiding principles and top priorities were support for Ukraine, strengthening Lithuania's security, an active foreign policy and active participation in the various forms of the European Union,” he said.
The results showed Nauseda won about three-quarters of the vote, far ahead of her rival, Prime Minister Ingrida Simonytė, from the ruling Fatherland Union party.
She conceded defeat late on Sunday night, congratulated Nauseda and promised to return to office on Monday.
“I still have a lot of confidence. People who believe in me are my biggest motivation to keep going. We will move forward and I will go back to work tomorrow and keep working,” she said.
Nauseda, a 60-year-old independent and former economist at Sweden's SEB bank group, won the first round of elections in May with 44 percent of the vote, short of the 50 percent needed for a landslide victory.
He told supporters he would remain committed to the defence of Lithuania.
“I think we have always moved forward and implemented very important decisions, especially regarding Lithuania's security,” he said.
Nauseda and Simonytė found common ground on defense spending, with both supporting an increase from 2.75% of GDP to 3%.
But they clashed over other issues, including whether to legalize it. Same-sex marriage.
Nauseda opposes the idea, arguing that such a union would be too similar to marriage, which the Lithuanian constitution recognises as between a man and a woman.
The Lithuanian president has a quasi-executive role that includes leading the armed forces and representing the country at EU and NATO summits.
However, the Prime Minister, together with the Government, sets foreign and security policy and can veto legislation.